1. Field of the Invention
The present invention relates to reference potential measurement, and more particularly, to a reference potential adjusting apparatus and a measurement apparatus including the same.
2. Discussion of Related Art
In general, an electrochemical analysis method uses a 3-electrode type measurement apparatus to analyze a material using electrodes. The 3-electrode type measurement apparatus is composed of three electrodes including a working electrode, a counter electrode, and a reference electrode. In detail, in a chemical analysis apparatus containing a solution in which oxidation-reduction reactions occur, an electrode that causes electrode reactions with a material to be measured is called a “working electrode,” and an electrode whose one side has a relatively large area or is made of a high reactivity material is called a “counter electrode.” Also, an electrode for monitoring the electrochemical potential of the solution to maintain the concentration in the solution constant of ions subject to the oxidation-reduction reactions is called a “reference electrode.” Also, a constant potential that is measured by the reference electrode is called a “reference potential.”
FIG. 1 is a circuit diagram illustrating a conventional 3-electrode type measurement apparatus 100. Referring to FIG. 1, the 3-electrode type measurement apparatus 100 includes a voltage supply unit 110, a variable resistor 120, a working electrode 130, a counter electrode 140, and a reference electrode 150.
The reference electrode 150 is provided to measure a reference potential of the 3-electrode type measurement apparatus 100. The reference electrode 150 drives a feedback circuit based on the measured potential of a solution to change a voltage applied between the working electrode 130 and the counter electrode 140. Thereby, the reference electrode 150 can maintain a constant reference potential so that the 3-electrode type measurement system 100 can stably operate.
In the conventional 3-electrode type measurement apparatus 100, the reference electrode 150 may be a standard hydrogen electrode (SHE), a saturated calomel electrode (SCE), an Ag/AgCl electrode, a Cu/CuSO4 electrode, or an Hg electrode, and the above-mentioned electrodes are made of materials capable of causing direct oxidation-reduction reactions with the solution. However, when the method of setting the reference potential using the conventional electrodes is applied to a bio sensor, etc., the following problems are generated. First, in order to manufacture a bio sensor, etc. using a semiconductor manufacturing method, an additional process for applying the above-mentioned materials is needed and also specific reaction areas should be added, which makes manufacturing of such a sensor product difficult. Second, since at least one ion in an aqueous solution should be the kind which can be oxidized or reduced to ions of a reference electrode material, the kinds of available solutions may be limited. Third, since the reference electrode is worn down due to oxidation-reduction reactions, the sensor's lifetime may be shortened. Fourth, the sensor may be sensitive to environmental factors such as temperature.
Accordingly, demands for an improved measurement apparatus capable of stabilizing a measurement system by easily setting a reference potential without causing the above-described problems are increasing.
Also, many sensors that are driven in a solution such as an electrolyte, other than the 3-electrode type measurement apparatus, require a stable operation environment and a more reliable apparatus for controlling a reference potential.